Refractory protection shield for continuous flow furnaces

ABSTRACT

A continuous flow furnace is comprised of a plurality of assembled sections including a roller power conveyor carrying products therethrough and having independently movable upper and lower tunnel sections joined along a horizontal parting line by high temperature alumina-silica mineral wool (Kaowool) packing and the packing is protected from erosion by contact of the moving products against its inner face by a ceramic protective shield hung from a plurality of inclined refractory pins and pin receiving apertures which permit the plates to move in response to produce contact yet not interfere with relative movement of the tunnel sections and/or the conveyor due to differential expansion and contraction.

United States Patent Cable et al.

REFRACTORY PROTECTION SHIELD FOR CONTINUOUS FLOW FURNACES [75] Inventors: Stephen J. Cable, l-lartville; Lee R.

Fuller, Canton; John H. Hothem, North Canton, all of Ohio [73] Assignee: Spartek Inc., Canton, Ohio [22] Filed: Aug. 29, 1974 [21] Appl. No.: 501,671

[52] US. Cl. 432/121; 432/244; 432/266 [51] Int. Cl. F27B 9/00; F27D 3/00 [58] Field of Search 432/121, 244, 246, 266

[56] References Cited UNITED STATES PATENTS 1,988,110 1/1935 Drake 432/244 2,872,174 2/1959 Lindquist 432/246 Primary ExaminerJohn J. Camby Attorney, Agent, or FirmGardiner, Sixbey, Bradford & Carlson [57] ABSTRACT A continuous flow furnace is comprised of a plurality of assembled sections including a roller power con veyor carrying products therethrough and having independently movable upper and lower tunnel sections joined along a horizontal parting line by high temperature alumina-silica mineral wool (Kaowool) packing and the packing is protected from erosion by contact of the moving products against its inner face by a ceramic protective shield hung from a plurality of in clined refractory pins and pin receiving apertures which permit the plates to move in response to produce contact yet not interfere with relative movement of the tunnel sections and/or the conveyor due to differential expansion and contraction.

9 Claims, 3 Drawing Figures Ico FIG I US. Patent Oct. 21, 1975 REFRACTORY PROTECTION SHIELD FOR CONTINUOUS FLOW FURNACES BACKGROUND Many ceramic products demand, as an essential step in manufacture, a heating or firing step. Examples of such products are brick, ceramic figurines, baked enamel parts, and so forth. Often the firing operation requires the application of different levels of firing temperature for different periods of time and additionally the fired products must be cooled subsequent to the firing operation so that when completed they may be handled as is customary in the particular industry.

In general the firing-operation is conducted in heated tunnel kilns wherein the product to be fired is deposited on some form of conveyance such as a kiln car and is pushed into the kiln. The kiln cars move slowly through the kiln and are heated to whatever temperature or temperature ranges may be required and after heating are allowed to cool as the kiln cars exit the tunnel. In many cases the whole process requires days of time from the initial kiln loading operation until removal of the product.

Quite recently there has been developed a form of roller hearth kiln where the products are carried in one continuous operation through the kiln on a roller conveyor. One example of such a roller hearth kiln is exemplified in U.S. Pat. No. 3,608,876 issued to Charles E. Leaich entitled Heat Treating Apparatus With Roller-Type Hearth.

As shown in U.S. Pat. No. 3,608,876 the apparatus is comprised of a plurality of unattached but operatively associated subcombinations which are related to define an elongated generally rectangular crosssectioned tunnel having a roller conveyor located therein in a horizontal plane. The upper and lower tunnel sections are related along horizontal parting lines which lie in the same plane as that of the horizontal roller conveyor and the longitudinal joints thus defined are packed with a refractory joint filler material (alumina-silica mineral wool) known by the trade name of Kaowool manufactured by the Babcock and Wilcox Company, Refractories Division, Augusta, Ga. 30903.

As further described in the noted patent, the conveyor and tunnel sections and related subassemblies are all so suspended that each may move freely with respect to one another to absorb the deleterious effects of movement caused by the differential expansion and contraction of the various components due to the heating or cooling steps being performed at various zones along the length of the tunnel.

While the described apparatus has met with considerable success, two difficulties that have been encountered are, first, the products do not always track true on the conveyor with the result that they contact the interior faces of the tunnel walls and severely abrade the Kaowool surrounding the rollers and located at the parting line with a result that the packing is torn out of the joint and the apparatus must be shut down with regular frequency to repack the joints. Secondly, continuous direct exposure of this alumina-silica mineral wool to the moving hot gases within the kiln casues a loss of strength in the individual fibers which makes the material more fragile, and thus, more easily removed by ;abrasion from the movement of the products through :and the movement of the hot gases within the kiln.

It is with these problems that the present invention deals and broadly it may be stated that an object of the invention is to provide a means for protecting a packed kiln joint from destruction caused by contact by products moving through and within the kiln.

More particularly the object of the invention is to provide a protective shield for a packed joint in a roller hearth kiln to protect the joint from damage by the products moving therethrough.

The noted objects and others not specifically enumerated, but readily apparent to those skilled in the art, may be accomplished by providing a protective shield along the joint defined between the upper and lower tunnel halves of the kiln said shield being comprised of a plurality of generally rectangular thin plates of heat resistant material, each plate having a lower scalloped edge and beveled shorter edges facing inwardly toward the interior of the kiln tunnel and having, further, a pair of spaced vertically elongated slot-like apertures adjacent each upper corner and a generally centrally located vertically elongated slot-like aperture larger in length and width than aforesaid pairs of apertures, at least the upper wall of each aperture being inclined downwardly from the kiln interior facing side of said plate to its opposite side, said plate being suspended from at least three hanger pins in said kiln wall, said pins being inclined downwardly into the wall at approximately the same angle of inclination as that of the inclined upper wall of each of said apertures.

Having described the invention broadly, attention is now directed to the appended drawings which, along with the following detailed description provides complete disclosure of a preferred form of the invention and wherein:

FIG. 1 of the drawings is a vertical sectional view through a rotary hearth kiln of the type disclosed in U.S. Pat. No. 3,608,876.

FIG. 2 is an enlarged partial sectional view of the joint between upper and lower kiln sections showing the protective plate of the invention, and

FIG. 3 is a partial vertical, enlarged elevational view taken along the line 3-3 of FIG. 2.

As shown in FIG. 1 the roller hearth kiln is comprised of an upper inverted U-shaped section 1 including walls 15, 16, and cover 19. The lower portion of the kiln is comprised of a U-shaped section 7 comprised of vertical sides 3 and 5 and a bottom 9, it being understood that these sections define an elongated tunnel of rectangular cross-sectional configuration as shown in the noted patent. The sections 1 and 7 are all suspended for independent movement from an overhead frame support designated generally as 20, this arrangement being fully described in said U.S. Pat. No. 3,608,876. Similarly suspended from frame 20 is a roller hearth comprised of a repetitive series of horizontally disposed rolls 14 which extend outwardly beyong the sidewalls 3 and 16 and 5 and 15 respectively. The roller ends are suspended in and driven for rotation by means fully described in said patent and the arrangement need not be described here in detail forming no part of the present invention.

The products 13, to be heat treated are supported upon and conveyed by the multiple rollers 14 into, through, and out of the elongated kiln tunnel.

As shown in FIGS. 1 and 2 the rollers 14 lie in a horizontal plane which is coincident with the horizontal parting lines defined between the upper and lower sidewalls 15, 16, and 3 and 5 of the respective upper and lower tunnel sections 1 and 7 so that the roller ends do not pass through any of the walls per se, but, instead pass through a refractory packing material 24,24 which is packed between the upper, step-shaped edges ofthe walls 3 and 5 and the mating inverted stepshaped lower edges 21,21 of walls 3 and 5. This packing seals the sidewalls against loss of heat through the joint yet permits rollers 14 to freely rotate and also permits relative movement between the various components as may be required to accommodate expansion and contraction of the components due to heating and cooling. As noted this packing is refractory material known as Kaowool (alumina-silica mineral wool) which is manually emplaced in the joint.

While the packing is satisfactory to seal the joint it is not as resistant to damage from frictional contact and impact as are the refractory sidewalls of the kiln sections 1 and 7.

While in the ordinary course of events the products 13 track along the roller hearth in orderly fashion there are instances where the products do not properly track on the roller hearth and as a consequence contact the kiln sidewalls 15, 16 above the surface of the rolls 14 and also contact the packed Kaowool 24,24 and are dragged there along with the result that the packing begins to deteriorate and loosen in the joint area. It has been found from experience that, when the kiln is operated on a continuous 24 hour day-to-day basis, the joint packing deteriorates from the combined effect of erosion by product contact and from erosion brought about by its direct exposure to the hot gases of the kiln interior to the point where it must be refurbished approximately every three to six months with an attendant loss of at least several days production to permit the kiln to cool to allow entry and repair, followed by re-heating to whatever given parameters govern its operation.

Attempts to rectify the stated problem were not fruitful until development of the present joint shields 30,30, as it being understood that shield is a duplication of shield 30 which will be described in detail.

As shown primarily in FIGS. 2 and 3, the joint shield '30 is comprised of a plurality of heat resistant refractory plates 21 of identical configuration which are hung from the sidewall 16 on rows of refractory pins 33,35. The plates are preferably rectangular in form having a longer dimension of about 7 inches from top edge to bottom edge, a side-to-side dimension of approximately 6 inches and a thickness of about one-fourth inch. Any abrasive resistant, high temperature resistant material will serve as the material from which the plates may be fabricated. As is clearly evident in FIG. 3, the side edges 23 and 25 of the plates 21 are beveled from the kiln face side outwardly. These beveled edges prevent the moving products from hooking against the plate edges as they move along the roller hearth on rolls 14 should the interior wall 16 not be precisely co-planar throughout the length of the kiln.

The lower edge 27 of the plate 21 is defined by a plu-. rality of spaced semi-circular cutouts 29 interdigitated with a plurality of pendent aprons 31 so arranged that the rollers 14 fit within the cutouts 29 and the pendent aprons 31 extend downward between adjacent rollers below the surface of the rollers 14 below the normal horizontal flow path of materials or articles being moved along the roller hearth as defined by the roller surfaces. Thus, any product on the hearth surface cannot hook under the plates as might be the case were the lower edge not scalloped or was disposed above the rollers.

As noted before, the plates 21 are suspended from the inside face of the sidewall 16 by means of a plurality. of a pair of refractory pins 33, 35, each pair of which pass through one each of a pair of slot-like apertures 37, 39, 37', 39 located at the upper corners of plate 21 and symmetrically located with respect to the vertical center-line thereof. These pairsof slots are all equal in size and are characterized by the fact that at least the upper arcuate end wall of each is inclined downward at an angle which conforms to the angle at which the respective pins 33,35 are driven into or otherwise affixed in wall 16. This angular cooperation between pins and 1 adjacent the upper corners of plate 21, only one slot of each pair, in the illustration, slots 37 and 37 are engaged with the pins 33,35. The multiple slots are provided to permit some selection in placement of the pins so that in the event a pin cannot be affixed for one reason or another in a precise spot in the wall 16 at a space ing receptive of a given pair of slots, it can be so placed as to be receptive at least one of the slots of each pair to suspend the plate from two points along its. upper,

edge.

Located below the row of pins 33, 35 is a second row of refractory pins 41. These pins are so spaced as to be disposed at the approximate center of each plate 21.

Pins 41 engage a further slot-like opening 43 in plate 21. This slot-like opening possesses all of the characteristics of slots 33,37 except that it is somewhat larger, than these slot-like openings.

The purpose of pins 41 and slot 43 is to stablize plate i 21 against an edgewise rocking motion when struckby a product so that even though the plate may move or rock slightly, it will not become disengaged from the pins 33,35 should such rocking occur. The width, of slot-like opening 43 however does permit some motion which is desirable to reduce frictional contact between a product and the plate as a stray product is directly along the roller hearth by rolls 14.

From the foregoing description it may be seen that there is provided a highly effective joint shield for roller hearth kilns and that various modifications will be ap-:

parent to those skilled in the art; all of which are within the spirit and scope of the invention as defined by the appended claims, wherein;

What is claimed is:

1. In a roller hearth kiln having freely, relatively movable upper and lower tunnel sections joined along longitudinal parting lines along each sidewall and having a plurality of horizontally disposed rollers extending through the joint formed along said parting lines and a packing means closing said joint; a shield means along i said joint to protect said packing from contact by prod-, I ucts moving along said rollers through the said kiln,

said shield means comprising a plurality of co-pl anar,

refractory plates movably suspended from the inner face of the sidewalls of the upper section of said kiln each of said plates being of generally rectangular con-r figuration and having beveled vertical edges and a lower edge disposed below the tops of said horizontally disposed rollers.

2. The combination as defined in claim 1, wherein the bottom edge of each of said plates includes a plurality of semi-circular cutouts and a plurality of interdigitated depending aprons, said cutouts and said aprons being in registry with the rollers of said roller hearth so that said aprons extend downward between adjacent ones of said plurality of rollers.

3. The combination as defined in claim 1, including suspension means for each of said plates, said means being comprised of a plurality of inclined pins on the inside wall of the upper tunnel section, said plates having at least a number of slot-like apertures corresponding to the number of said pin and wherein each aperture has an inclined wall disposed at the same angle as the angle of inclination of said pins relative to said inner wall of said kiln section.

4. The combination defined in claim 3, wherein the number of pins associated with each refractory plate is three, two each of which are disposed in a common horizontal plane and the third of which is disposed in a horizontal plane which is lower than said first mentioned horizontal plane, and said plate has a corresponding number of slot-like apertures for registry and engagement with said pins.

5. The combination defined in claim 4, wherein the lowermost slot-like aperture in said plate is larger than the two upper apertures therein.

6. 'For use in protecting a joint in a kiln wall having a longitudinally extending packed joint, a shield comprised of a generally rectangular flat plate of high temperature resistant material, said plate having a sealloped lower edge and beveled side edges and further having a plurality of apertures therein said apertures defining slots having a longer dimension parallelling the sides of the plate and a top marginal wall inclined on an angle relative to the inner and outer faces of said plate.

7. A shield as defined in claim 6, wherein said plate has at least three slot-like apertures at least two of which are located in close proximity of the upper corners thereof and the third of which is located at the approximate center of said plate.

8. A shield as defined in claim 6, wherein said centrally disposed, slot-like aperture is larger than the said other two apertures;

9. A shield as defined in claim 8, wherein said plate is provided with adjacent pairs of slot-like apertures in close proximity to each upper corner thereof. 

1. In a roller hearth kiln having freely, relatively movable upper and lower tunnel sections joined along longitudinal parting lines along each sidewall and having a plurality of horizontally disposed rollers extending through the joint formed along said parting lines and a packing means closing said joint; a shield means along said joint to protect said packing from contact by products moving along said rollers through the said kiln, said shield means comprising a plurality of co-planar refractory plates movably suspended from the inner face of the sidewalls of the upper section of said kiln each of said plates being of generally rectangular configuration and having beveled vertical edges and a lower edge disposed below the tops of said horizontally disposed rollers.
 2. The combination as defined in claim 1, wherein the bottom edge of each of said plates includes a plurality of semi-circular cutouts and a plurality of interdigitated depending aprons, said cutouts and said aprons being in registry with the rollers of said roller hearth so that said aprons extend downward between adjacent ones of said plurality of rollers.
 3. The combination as defined in claim 1, including suspension means for each of said plates, said means being comprised of a plurality of inclined pins on the inside wall of the upper tunnel section, said plates having at least a number of slot-like apertures corresponding to the number of said pin and wherein each aperture has an inclined wall Disposed at the same angle as the angle of inclination of said pins relative to said inner wall of said kiln section.
 4. The combination defined in claim 3, wherein the number of pins associated with each refractory plate is three, two each of which are disposed in a common horizontal plane and the third of which is disposed in a horizontal plane which is lower than said first mentioned horizontal plane, and said plate has a corresponding number of slot-like apertures for registry and engagement with said pins.
 5. The combination defined in claim 4, wherein the lowermost slot-like aperture in said plate is larger than the two upper apertures therein.
 6. For use in protecting a joint in a kiln wall having a longitudinally extending packed joint, a shield comprised of a generally rectangular flat plate of high temperature resistant material, said plate having a scalloped lower edge and beveled side edges and further having a plurality of apertures therein said apertures defining slots having a longer dimension parallelling the sides of the plate and a top marginal wall inclined on an angle relative to the inner and outer faces of said plate.
 7. A shield as defined in claim 6, wherein said plate has at least three slot-like apertures at least two of which are located in close proximity of the upper corners thereof and the third of which is located at the approximate center of said plate.
 8. A shield as defined in claim 6, wherein said centrally disposed, slot-like aperture is larger than the said other two apertures.
 9. A shield as defined in claim 8, wherein said plate is provided with adjacent pairs of slot-like apertures in close proximity to each upper corner thereof. 